Infinitely variable ratio transmission mechanism



Dec. 4, 1956 R. A. GILBERT 2,772,575

INFINITELY VARIABLE RATIO TRANSMISSION MECHANISM Filed April 18, 1955 3 Sheets-Sheet l g E J r F 2, 4 B* B 6 f 82 O lv EL H H J G ii lNvENToR E I RONALD A. Gmsea'r ATTORNEY R. A. GILBERT Dec. 4, 1956 INFINITELY VARIABLE RATIO TRANSMISSION MECHANISM Filed April 18, 1955 3 Sheets-Sheet 2 INVENTQR RONALD A. GILBERT wage, $4M -1 Math ATTORNEY Dec. 4, 1956 R. A. GILBERT 2,772,575

INFINITELY VARIABLE RATIO TRANSMISSION MECHANISM Filed April 18, 1955 s sheets-sheet s INVENTQR RONALD A GILBERT ATTORNEY f f 1 if INFINITELY This invention relates to infinitely variable-ratio transmission mechanism of the kind'comprising a shaft on which are mounted, so as to be capable of moving'a'xially but not rotating thereon,a number ofspaced discsLt-he opposite faces of each of which lie on opposite s'idesof a plane normal to the axis of the shaft'andprogressively approach that plane from their inner to' their outer circumferential portions, as bybeing of wide angle frus'to conical form, and at least one other shafthaving its" axis parallel to that of the first shaft and carrying discs having thickened circumferential edge portions constituting riblike' parts which lie between and make driving-engagement with the discs on thefirst shaft, resilient means tending always to 'press the discs on one shaft (hereinafter for convenience called the main shaft) axially-towards one another and therefore into close driving engagement with the discs on the other shaft (hereinafter forconvenience called a layshaft), andmeans for moving the shafts toward and away from one'another so'- as o vary the transmission ratio as between them. a a I Usually a set of discs of oneof the two forms referred to is mounted on themainshaft and-will beengaged'by two or more sets of discs of the other form'mounted'respectively on two or more'layshafts' evenlya'ngularly spaced about the axis of' the main shaft-and'arranged to be simultaneously and similarly moved towards and away from the axis of the main shaft so -that the ratio of transmission between" the'main shaft and "each "of the layshafts is the same at any moment. In such tra'nsmission gearing, of which atypical example is described in the specification of British Patent No. 671,561) the'ilay shafts are connected bytransmissiongearing to'acommon shaft coaxial with-the mainshaft so that the two coaxial shafts constitute'in eifectthe-input and'output shafts of the transmissionmechanismas a whole; I

in transmission mechanism of the general kind referred to as hitherto proposed the eifective forceaof the resilient means automatically becomes-less withemovement of the layshafts or layshafts away from the axis of the main shaft since thediscs on the'maim shaft are then permitted to move towards one another, and vice versa. According to the present" inventionfan infinitel'y 'variable ratio transmission mech'anisni'offthe kindfreferred to includes in combination with the "resilient m ean's for maintaining the transmission disc'sin' driving engagement,

apparatus arranged tobe operated simultaneouslyr with the control mechanism for moving the mainand layshafts towards and away from one another to vary the effective transmission ratio of the transmission mechanism and acting on the resilient means in such manner as to modify or control in some desired manner the force exerted by the resilient means on the disc or discs when such discs are moved under the action of the resilient means or against such action.

The apparatus acting on the resilient means and operated simultaneously with the control mechanism for varying the efiective transmission ratio may be so arranged as to tend to maintain the'force'exerted by the resilient means on the discs substantially constant over the whole range of transmissionrratios or so as to cause the force exerted by :the resilient means on the discs. toivaryxin accordancetwith some. predeterminedlaw, and in I the latter case'would usually. serve to reduce theivariations'in the'force. exerted by the resilient means on the1discs whichwwould occur'if theapparatus controlling the resilient-means weremot present; p; :1 .1 The resilient means will; usually be in the form. ofia spring or springs: acting on the discs oon themainishaft to maintain'them in driving engagementwith the. discs on the layshaft or layshafts, in whicli caseithe'apparatusfor controlling the reffectiverforce exerted-by iheaspring or springs on the discs will comprise a movable. abutment'for the end or ends, of the spring or springs remote frdjmthe discs.; In this case an operative :connection is provided betweenthe control; mechanism for varying the transmission ratio and thelabutment by "which the abutment is moved in -the ,requiredsense with, changes in the gear ratio. Thus in one convenient example,-; inwhich the resilientmeans comprises; one or more helical compression springs arrangedicoaxially with the main shaft-and ,acting,- -at -one;end upon the discs, thereon and at th e o he nd up n a m l a u men er ed o x al y with'the spring or springs, the abutment may be arranged to; rock through a-predetermined angle about the axis of thespring o pringsV-an sbe eon 'e to e s me mech ni mcf 'r, va y ng the miseionre i a o eso rocked y vemen f s q e n r me hani m m ns bein p d whereby; the abu ment is a sed to nqv axially W 'Q These :l tter. rm n fl r n gh C mprise -for example, quick-pitch -;screwthread mechanism or cam and followermechanismt fl a y 1 One construction accordingjto the -inventi0n';is illustrated byway of'example and'tosomeextent diagrammaticallyin the accompanyingdrawings, in-which: H I Figure; 1;,is a sectional side'elevation of the transmissi nzm h' nism, .t x; e I :1

Figure 2 is ajsomewhat diagrammatic end view showing t-hejgeneral -arrangement of the; discs; and the man er in which h rm to a y the e i e o v 1 f Eigure 3 is an end elevation partly in cross-se tion'in the pl f fiF re nd 1. I a v F gur s, 4 n v 5 a sm l v w w ng the fine e ;tion of cam and roller; mechanism embodied in the co nstruct ion'shown. g .s l; 1 h var le t o t ens i s eni h n emi Sh w :in th omp nyi d wi s o ie s ne n ei which; is carr d n ta le. b r ngs ime rshe, on w ich a e;mou t d, o th t-they s an S i QL Je Y ;thereon;.-bu not; rotate fl YlY t ere a t iesie' spacEeddiscs-iB :each so formed -as tov proyidegadja 'ent eitsae ge a m poort whiehi a sli nt yigreete -th ekness than the adjacent portions; Pivotally supported withinp lea n A101 xe 3 'eh a e e ye xr cumfcerentia lyo spaced ar und. th AX -th a l-$14??? B, a n llelito hi axis? a v three e-ar sCea h havins-moun e ther n. upon n. xi Q i a rebut iepl eed Ir nt a qe ated iyg 'l c n om ab e; aysh-aft C3 on which are mounted, so as to slide u trjn gt rota eirelet xe y;the et e: ser esont slisas :Dwh a o W wide angle frusto-coriical faces. extend The discs D into the spaces between the discs B to make driving engagement with the rim portions thereof all in a manner well-known in variable ratio transmission mechanism of the kind in question. Each of the layshafts C is connected by similar gearing '(not shown), including a gear wheel coaxial with the pivotal axis C of its carrier C, to a common shaft (also not shown) coaxial with the main shaft B so that the main shaft and the common shaft referred to constitute in effect main input and output shafts. As so far described the transmission gearing -is of well-known type and no more detailed dc.- scription thereof is therefore given.

Two of the carriers C have rigidly connected to them at one end arms E While the third carrier has rigidly connected to the same end thereof an arm .E as shown most clearly in Figure 3, the arms E and E as shown extending radially with respect to the axes C The three arms, E, E, E are connected by links F to lugs F on a ring P which is mounted in the casing A so as to be capable of rocking about the axis of the main shaft B and has at one end an internal flange P which bears on the outer race of a thrust bearing G the inner race of which is mounted on a sleeve G rigid with the shaft B. The arrangement is thus such that when movement is imparted to the arm E as by means of a control member indicated at E this causes rocking of the ring F and hence pivotal movement of each of the arms E corresponding exactly to the pivotal movement of the arm E By operation of the member E therefore, the three carriers C can be caused to rock simultaneously and similarly so as to move the disc D inwards and outwards in relation to the axis of the shaft B to vary the gear ratio of the transmission mechanism in wellknown manner.

The discs B lie axially between a rigid plate B secured to the shaft B and a second rigid plate B which is capable of sliding on the shaft B but not rotating thereon and is acted upon by the inner race H of a thrust bearing H acted upon through a thrust member H 'by an a'butment member I at one end of a multiple spring assembly comprising three helical springs generally indicated at J The other end of the spring assembly 1' acts upon an abutment K which is mounted so that it can move in a direction parallel to the axis of the shaft B for the purpose of maintaining a desired degree of compression in the spring assembly. The abutment K is in the 'form of a ring from which project in a direction away from the spring assembly I three l-shaped cam members K extending through slots in the flange F Mounted on a tubular member L rigid with the casing A is a ring L from which project towards the ring F three lugs L carrying rollers L arranged so as each to engage one side of one of the V-shaped cam members K as shown most clearly in Figures 4 and 5. The ring F is similarly provided with three lugs 16* carrying rollers P which engage the other sides of the V-shaped cam members K The two sides of each V-shaped cam member K are thus engaged respectively by a roller L mounted upon a stationary axis and a roller F mounted on the ring P which is movable about'the axis of the main shaft and is so moved with variations in the positions of the carriers C to vary the transmission ratio.

It will be apparent that the movement imparted to the ring F and hence to the rollers F will, by causing the rollers F and L to move towards and away from one another in the circumferential direction, cause axial movement of the abutment K and hence control the compression of the springs of the spring assembly J in a manner related to the gear ratio being transmitted and in accordance with a law which can either be a subtantially straight line law or some other law, depending upon the formation of the surfaces of the l-shaped cams K Thus in a typical example it is possible to ensure that,

The outer race H of the bearing H is 4 irrespective of the gear ratio being transmitted and hence of the degree of separation of the discs B by reason of the entry between them of the discs D, the axial force exerted upon the discs B by the spring assembly remains substantially constant. Alternatively the force exerted by the spring assembly upon the discs B may be caused to vary in accordance with some predetermined law so that the pressure with which the discs B are forced towards the discsD can always be approximately that which is appropriate to the gear ratio and/or to the power being transmitted.

In the above description constructional details, apart from those associated with the features in which the gear according to the invention differs from known gears, have been omitted for the sake of brevity.

What I claim as my invention and desire to secure by Letters Patent is:

1. An infinitely variable ratio transmission mechanism including in combination a main shaft, a series of transmission discs mounted to slide but not rotate on the main shaft, at least one lay shaft parallel to but displaced laterally from the main shaft, a series of transmission discs on the lay shaft and extending into the space between the discs on the main shaft, the surfaces of the discs on one of the said shafts being or" generally frusto-conical form, and engaged by rim portions of the discs on the other of the said shafts, an abutment, resilient means tending to force the transmission discs on the main shaft toward one another, said resilient means comprising a helical spring assembly arranged 'coaxially with the discs on the main shaft and acting at one end upon such discs and at the other end upon said abutment, said abutment being arranged coaxially with the spring assembly, control mechanism for moving the main and lay shafts toward and away from one another to vary the effective transmission ratio of the transmission mechanism according to a predetermined law entirely independent of variations in the torque being transmitted, a control ring interconnected with the transmission mechanism and arranged coaxially with and capable of rocking about the axis of the spring assembly, cam'means between the control ring and the adjacent spring abutment whereby such rocking movement of the control ring causes axial movement of the spring abutment to control the force exerted by the resilient means on the discs, as such discs move toward and away from one another.

2. An infinitely variable ratio transmission mechanism as claimed in claim 1, in which the cam mechanism comprises V-shaped cam members on the abutment ot' the spring assembly, and a fixed roller and a roller carried by the control ring arranged to engage the opposite sides of eachV-shaped cam member whereby movement of the two rollers associated with each cam member towards and away from one another causes axial movement of the abutment.

References Cited in the file of this patent UNITED STATES PATENTS 1,806,984- Prout May 26, 1931 2,586,260 Rennerfelt Feb. 19, 1952 2,623,396 Beier Q. Dec. 30, 1952 FOREIGN PATENTS 257,792 Great Britain Sept. 9, 1926 

